The Smell Compatibility Theory: Can You Sniff Out A Potential Partner?

As the old adage goes, love may well be blind from our sight — but not our senses. Cutting-edge research reveals the powerful role of scent in our subconscious decision making. The Smell Compatibility Theory suggests that attraction may go beyond looks, rooted in the scents we naturally give off.

In this article, we explore the fascinating role of immune system compatibility in the pheromone phenomenon, examining how scent influences sexual chemistry, sleep, and relationships.

What could this connection reveal about your health—and even your dating history?

• Natural body aroma is a significant factor in attraction and partner choice.
• Your scent carries subtle genetic cues that may indicate compatibility.
• Being aware of the role that scent plays could potentially enrich romantic connections.

How does your immune system influence your love life?

The smell compatibility theory can be simply explained as a direct link to your DNA and how it makes you genetically compatible with another person.

The idea of a genetically compatible smell is based on the theory that people may be subconsciously drawn to partners with different major histocompatibility complex (MHC) genes, that’s a group of genes that code for proteins that help build the immune system.

In this way, this perception of scent may also be historically significant as an evolutionary adaptation to avoid inbreeding and to ensure the offspring have strong immune systems. Other mammals, as well as fish and birds, share this olfactory characteristic.

The 'Sweaty T-shirt' experiment

This experiment tested the theory and was subsequently named the "sweaty T-shirt". While it may sound off-putting, the study provided some pretty conclusive results. Biologist Claus Wedekind described that the purpose of the experiment was to find evidence behind MHC-related scent preferences.

In the study, men wore T-shirts for two consecutive nights without using any scented products. Women were then asked to smell the shirts and rate their attractiveness. The results simply revealed that women were more attracted to the scents of men whose MHC genes differed from their own.

Conversely, in a study that investigated men's preferences for women's body odours in relation to MHC similarity, the findings indicated that men did not prefer the scents of women who were MHC-dissimilar, MHC-heterozygous, or who possessed rare MHC alleles. Put simply, this suggests that, unlike women, men's attraction to female body odour may not be significantly influenced by MHC compatibility. 

Influencing our scent preferences: other factors at play

There are other factors that warp the scent perspective. For instance, hormonal changes, such as those occurring during the menstrual cycle, can affect women's sensitivity to male scents. Additionally, the use of hormonal contraceptives has been shown to alter women's preferences, sometimes leading them to favour scents of men with similar MHC genes.

Diet, health status, and other lifestyle factors can show up, affecting a person's natural scent. For instance, certain foods, medications and even emotions have been shown to change body odour, for better or for worse, potentially making them more attractive to others.

There may be some added layers to this common phrase. Researchers found that people with diets containing a high proportion of meat products tend to smell generally ‘worse’ than those on a mainly vegetable diet.

Unnatural fragrances have infiltrated the market over the years, perhaps in a bid to ‘corrupt’ our navigational sense of attraction to one another. Some may go as far as to say that chemically laden products could affect our subconscious choices of attraction. A study published in Frontiers in Psychology found that while individuals could distinguish between natural body odours, the introduction of fragrances did notably affect this ability.

To this point, there are also perfumes specifically containing pheromones on the market, which could be adding to the onslaught on our senses. Interestingly, the most frequently occurring lab-produced pheromone present in these products, androstenone, has a polarising effect — some people find it appealing, while others describe its scent as unpleasantly similar to urine or sweat. 

Does your partner’s scent help you sleep?

The curious intersection of scent and sleep for relationship health has taught us that there’s more to scent than simply physical attraction. But, it also has a surprising link to sleep. Research in Psychological Science found that people sleep better when exposed to their partner’s scent, and this can also happen if they aren’t physically there. Therefore, it would appear that a familiar smell can offer a sense of security and calm, making it easier for a person to drift off.

That is, for some, of course. Because, what happens when one partner’s bedtime habits, such as snoring, fidgeting and different temperature preferences — disrupt the other’s peace? That’s where the idea of “sleeping apart together” comes in. Some couples are choosing to sleep separately to get better quality rest, without sacrificing intimacy. Instead of a sign of relationship trouble, it might actually be a practical solution for those with mismatched sleep needs. You can learn more as we discuss the pros and cons in our dedicated article.

How may the MHC be overlooked in the world of online dating?

In a modern digital dating culture, based primarily on aesthetics and superficial attributes, the significance of the MHC on our dating choices could be taking a backseat. In meeting face to face with someone, the attraction based on the MHC would be more likely to take effect.

Some match services have gone a step beyond the average as a result, attempting to incorporate genetic testing to address this gap. However, the efficacy of these approaches is still up for debate. 

Scent and sexual chemistry

Research indicates that natural body scents can influence sexual attraction and arousal. Compounds like androstadienone, found in higher levels in male sweat, have been shown to affect women's mood and sexual arousal. Studies suggest that exposure to androstadienone can enhance sexual desire and arousal in women.

In a broader sense, certain body odours can carry emotional information. For example, compounds from breastfeeding women have been found to increase sexual motivation in other women and alter the timing of ovulation.

Scent and same-sex couples

Research into the role of scent in same-sex attraction is ongoing, with some studies suggesting that natural body odours and the MHC may also influence partner preferences among same-sex couples.

A study found that homosexual men exhibited hypothalamic activation patterns similar to heterosexual women when exposed to a testosterone derivative present in male sweat, suggesting a biological basis for scent-based attraction related to sexual orientation.

Evidence from other sources suggests that factors away from the MHC may also be at play in terms of attraction in same-sex couples. A large-scale genome-wide study suggests that genetics play a part in same-sex sexual behaviour, though it’s far from the whole story. Researchers identified multiple genetic variants that each exert a small influence, with genetics estimated to account for only around 8 to 25% of the variation, leaving a far larger role for other biological and social factors.

Key takeaways on scent and compatibility

• Scent has been explored as a subconscious matchmaker – Our sense of smell may influence attraction more so than we realise, with MHC-related scents playing a role in detecting genetic compatibility.
• The evolutionary advantage of scent-based selection – Preferring partners with different MHC genes could be nature’s way of strengthening immune systems in future generations.
• Hormones, lifestyle, and external factors – Contraceptives, diet, and even stress can alter how we perceive scent, sometimes changing the natural flow of attraction patterns in unexpected ways.
• Fragrance vs. natural scent – While perfumes with an excessive amount of synthetic and lab-made aromas can be pleasant and may even add appeal on a personal level, they could also be guilty of overriding the deeper biological cues that signal compatibility.
• Scent, intimacy, and sleep – A partner’s natural odour has been linked to improved sleep, offering a sense of security even when they’re not physically present.
• The digital dating disconnect – Modern dating apps prioritise looks over scent, potentially overlooking an essential factor in long-term attraction.

For purposes of relaxation, attraction, or simply elevating your environment, scent is integral to the very fibres of our wellbeing.

Try natural fragrances for the body and home with The Nue Co. FOREST LUNGS - Stress Relief, designed to calm the nervous system and reduce stress, or The Nue Co. Water Therapy Fragrance, inspired by the ocean to create a sense of deep tranquillity. Set the mood in your space with the Vitruvi Charcoal Stone Diffuser, an elegant way to disperse essential oils that soothe the senses.

Have Run Clubs Become A Dating Day Activity?

Read more

The Science Of Connection: Are We Oxytocin Deficient And Is Kissing Good For You?

Read more

Biohack Your Sex Life

Read more

Do You Need A Hug? The Science Of Twelve Hugs A Day For Healthy Human Connection

Read more